1. Field of the Invention
The present invention relates to an automatic starting device for an engine, which is capable of stopping fuel supply when the engine does not need to be driven during an operation and, in addition, of quietly and quickly restarting the engine when a re-acceleration request is made by a driver, in the engine for a vehicle.
2. Description of the Related Art
In order to improve fuel efficiency of a vehicle, a technology of stopping fuel supply to an engine during idling or deceleration during which the vehicle does not need to be driven has been disclosed.
In general engine control, the fuel supply is stopped during deceleration. As an engine rpm is gradually reduced, a clutch is released at a predetermined engine rpm which is larger than an engine rpm during idling. At the same time, the fuel supply is restarted to perform idle control, thereby preventing an engine stall.
Further, as a technology for improving the fuel efficiency, the following is disclosed in JP 08-189395 A (hereinafter, referred to as Patent Document 1), for example. According to the technology disclosed in Patent Document 1, the fuel supply is stopped unless a driver presses down an accelerator pedal. On the other hand, when the driver presses down the accelerator pedal for re-acceleration, the clutch is engaged to restart the fuel supply. If the rotation of the engine is stopped at this time, the engine is restarted by a starter so as to prevent idling, which does not contribute to drive of a vehicle, as much as possible.
Moreover, JP 2002-221059 A (hereinafter, referred to as Patent Document 2) discloses the following technology of restarting the engine. While the accelerator is OFF during deceleration, the fuel supply is stopped. When a pressing amount of a brake pedal is reduced, it is predicted that the driver performs re-acceleration. Therefore, when the engine rpm becomes equal to or less than a resonance rpm, the starter is driven to restart the engine. In Patent Document 2, if recovery from a fuel-supply stop state is made in a region where the engine rpm is small, the engine and a vehicle body resonate with each other. Therefore, when the engine rpm becomes the resonance rpm during the deceleration, auxiliary machines such as a generator and an air conditioner are temporarily driven to allow the engine rpm to quickly pass through a region of the resonance rpm.
JP 2001-317439 A (hereinafter, referred to as Patent Document 3) discloses the following technology of restarting the engine by using the starter. The starter includes a circuit for operating an electromagnetic solenoid for pushing out a pinion gear and a circuit for driving a motor, which are separately provided so as to be independently operated. During an idle stop of the vehicle, the pinion gear is placed in a standby state while being meshed with a ring gear. Simultaneously with a starting operation performed by the driver, the motor is driven to rotate the pinion gear to perform cranking, thereby restarting the engine.
According to the method disclosed in Patent Document 1, however, in the case where the rotation of the engine is stopped, the engine is restarted using the starter. Therefore, each time the accelerator pedal is pressed down during the deceleration, there is a fear in that meshing noise is generated in the starter.
Moreover, according to the method disclosed in Patent Document 2, in the case where a general starter, specifically, a starter including the pinion gear which is pushed out to be meshed with the ring gear, is used, if the starter is driven immediately after the engine rpm becomes equal to or less than the resonance rpm, there is a fear in that the gears fail to mesh with each other to generate big foreign sounds.
Further, Patent Document 3 merely discloses a method of using the starter, in which the push-out of the pinion gear and the motor drive are separately performed, after the vehicle is stopped. Therefore, Patent Document 3 does not cover the technology of expanding the region where the fuel supply is stopped from the deceleration of the vehicle to the idling so as to further improve the fuel efficiency.